Process and device for treatment of a web, particularly a textile web

ABSTRACT

A process for dyeing a textile web, in which the textile web is continuously guided through a trough that contains the dye bath, and subsequently passes through a pair of squeezing rollers. The line force of the pair of squeezing rollers is adjusted as a function of the length of textile web (L) that has passed through, with the aim of achieving a uniform amount of dye applied over the length of the textile web, per surface unit of the textile web.

BACKGROUND OF THE INVENTION

The present invention relates to processes and apparatus for treating atextile web with a treatment liquid containing a treatment medium, suchas a dye bath, in which the textile web is continuously guided through atrough containing the treatment liquid, and subsequently passed througha pair of squeezing rollers.

One such process and corresponding apparatus are known from thereference “Melliand Textilberichte” 1/1989, pages 46 to 52, particularlypage 52, FIG. 23. The trough and the pair of squeezing rollers togetherform a conventional foulard. In the known embodiment, a system for“concentration regulation,” shown schematically, can be seen in thetrough of the foulard, which is supposed to be able to take place“locally (edge/center) and/or laterally (run-off/tailing).” However,there is no information in the reference to indicate what is to be donewith the concentration values that are determined. The pair of squeezingrollers of the foulard is entirely neutral, i.e. it is shown without anyreference to a control mechanism.

The present invention begins from consideration of problems in thecontinuous dyeing of textile webs on a foulard. In this connection,particularly in the case of substantive and reactive dyes, the effectoccurs that water, as the solution and transport medium, is absorbedmore slowly or more rapidly by the web as it passes through the troughof the foulard, relative to the dye components in the dye bath. If theweb absorbs water more rapidly, the dye bath loses water and theconcentration of dye becomes higher. This means that the depth of shadeincreases, i.e. that the beginning of the web is clearly dyed a lightercolor than the end of the dye lot in question.

A typical example for this case is dyeing viscose with reactive dyes.Initially, viscose swells very much and entrains a lot of water from thedye bath.

However, the reverse case also occurs, that a certain textile webabsorbs more dye from the dye bath. This means that the beginning of thedye lot is dyed with a greater depth of shade.

When dyeing with reactive dyes, another cause for a nonuniform dyeresult over the length of the web is the tendency of reactive dyes tohydrolyze. Hydrolyzed reactive dye is no longer available for the actualdyeing process, and can therefore lead to concentration changes ofreactive reactive dyes.

Color changes over the length of the web are also referred to as“tailing.” As a rule, they proceed according to a positive or negative efunction and end in a state of equilibrium; after this equilibrium isreached, no further changes take place. Changes over the length of theweb can be influenced not only by the properties of the fiber material,but also by physical properties such as strong water absorption of theweb and swelling processes.

Although the causes of tailing are essentially known today, the problemcontinues to exist in practice and the initial lengths of some dye lotsstill have to be sold as seconds or have to be rejected entirely. Thesolution approaches tried until now have not been very successful. Thesesolution approaches were, for example, to use dyes with a low affinityand/or hydrolysis constant, to reduce the temperature in the dye trough,or also to minimize the bath content in the dye trough.

In many cases, all these solution approaches reach clear limits,particularly in the important case of dyeing viscose with reactive dyes,which was mentioned, where starting lengths on the order of several tensof meters show color deviations which result in spoilage. Since shorterand shorter lengths of dye lots are being demanded today (down to aslittle as a hundred meters), there clearly is an urgent need to addressthis problem. The several tens of meters of starting length which cannotbe used represent too high a proportion of damaged goods.

SUMMARY OF THE INVENTION

The present invention is directed to the task of providing a process andapparatus for treating a textile web with a treatment liquid containinga treatment medium such that the problem of tailings is avoided, or atleast reduced.

A central idea in this invention is to balance out the change inconcentration of the dye bath which takes place in the foulard trough atthe beginning of the pass of a dye lot, by controlling the applicationamount of the dye bath. If the concentration in the foulard basinincreases, the squeezing rollers are set to impinge more strongly uponthe web, thereby reducing the amount of treatment liquid which remainson the textile web. This counteracts an overly great depth of shade.Vice versa, if the concentration of treatment medium in the foulardtrough drops, the application amount is increased by a correspondingadjustment of the pair of squeezing rollers, in order to keep the depthof shade at the desired value.

The invention works in two steps. First, a test textile web length isallowed to pass through at a line force of the pair of squeezing rollersthat is kept constant, in order to determine the concentrationprogression in the trough over the length of the textile web. Therelationship between a concentration change and the line force changerequired to balance it out is determined in advance, either bycalculations or by experiments, and is stored in memory in theregulation device. If the concentration of treatment medium in thetrough drops after the first segment of the textile web has passedthrough, the line force is reduced by a certain amount, so that moretreatment liquid and therefore also more treatment medium remains on thetextile web, in order to balance out the concentration drop in thetreatment liquid. The same holds true analogously if the concentrationof the bath in the trough initially increases. This concentrationprogression and the resulting reference progression in the line forceover the textile web length which is required to balance it out, inorder to apply a uniform amount of treatment medium to the textile web,are stored in memory. When the subsequent production textile weblength(s) now pass(es) through, the line force progression over thelength of the textile web is regulated to the reference progressionstored in memory. The determination of the concentration progressiononly has to be made once for a specific fabric, a specific treatmentliquid, and specific other treatment parameters such as temperature andworking speed. All other lots can be treated using the results stored inmemory.

The result, in other words the reference progression, can remain storedin memory in the device, if the test run and the subsequent productionruns all take place on the same device.

An arrangement for amount-controlled application of sizing to a textileweb is known from U.S. Pat. No. 3,207,125 (the contents of which areincorporated herein by reference), which also works with a foulard-typeapplication device, and contains a trough for saturating the textile webwith the sizing and a pair of squeezing rollers provided directlyafterwards, to adjust the amount of liquid applied. The electricalresistance at the textile web is continuously measured on a lengthsegment between the pair of squeezing rollers and a measurement roll.The electrical resistance in the web depends on the specificconductivity of the bath and the amount of bath applied. If theinfluence of a changing conductivity can be eliminated, the measuredresistance value is a measure for the amount applied, and therefore ofthe amount of sizing applied per surface unit. In order to eliminate theinfluence of changes in the conductivity of the bath, the conductivityis measured in the trough, on a random sample basis, and if deviationsoccur, the resistance signal between the pair of squeezing rollers andthe measurement roll is adjusted. The conductivity measurements in thetrough therefore serve only to check the bath properties, not to controlthe line force of the pair of squeezing rollers. This control takesplace rather via the resistance of the length segment of the web in themeasurement section, where a change means a change in the amountapplied. If a deviation from the predetermined reference value occurs,the amount of liquid applied is subsequently adjusted by setting theline force of the pair of squeezing rollers.

Control of the line force of the pair of squeezing rollers of a foulardis known from European Patent 411 414 B1. However, here control takesplace as a function of the calorimetrically determined color of thetextile web, which is still damp, after it leaves the pair of squeezingrollers.

Another aspect of the invention is to determine the reference curveindependent of the production site, in a laboratory or technical-scalefacility, and to record it on a data medium that is made available, forexample, in the form of a card for a certain material of the textile webor a certain treatment of the web, and handed over to the finisher. Thefinisher then only has to insert the data medium into his/her controldevice and can run the lot without having to determine the concentrationprogression of the initial length in advance and having to determine thereference curve for the line force over the length of the textile web.In particular, the data medium can be easily duplicated and madeavailable for use at several production sites.

In another embodiment of the invention, the concentration change in thetrough of the foulard as the textile web passes through is still takeninto account. However, this is not done in regulated manner, but ratheraccording to a fixed, predetermined progression. In other words, theconcentration changes which occur on certain textile webs during certaintreatments are taken into account in simplified form, on the basis ofempirical data.

The line force progression over the length of the textile web can onlyapproximate the “theoretical” line force progression resulting from theactual concentration change in the trough, but practice has shown thatapproximations can be found that eliminate the deviations of thetreatment result from the ideal value, in other words the colordeviations, for example, to such an extent that in practice, for exampleusing the eye, no differences can be determined.

The theoretical line force progression over the length of the web isapproximated in linear manner, or in linear manner piece by piece,because this type of control is the easiest to implement.

BRIEF DESCRIPTION OF THE DRAWINGS

Several embodiments of the invention are shown in the drawings, inschematic form, in which:

FIG. 1 shows a schematic side view of a foulard which can be controlledon the basis of concentration;

FIG. 2 and 3 show corresponding views for implementing a first exemplaryembodiment of the invention;

FIG. 2a and 3 a show related diagrams;

FIG. 4 shows a view of a second embodiment of the invention,corresponding to FIG. 1;

FIG. 4a shows a corresponding diagram.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a device, designated as a whole as 100, for dyeing atextile web 10, for example a lining or blouse material made of viscose,using reactive dyes, which works independently of the length of thetextile web 10 that has passed through, only as a function of theconcentration of the bath. Device 100 includes a foulard 1, whichcontains a trough 2, in the usual manner, which is filled up to a bathsurface 3 with dye bath 4, which represents the treatment liquid. Thetreatment medium is the dye contained in the treatment liquid, in anamount proportional to the amount of liquid. A rotating deflectionroller 5 is arranged in trough 2, located entirely below bath surface 3.Above bath surface 3, on the right, outside trough 2, a pair ofsqueezing rollers, designated as a whole as 7, is provided, composed ofa top roller 8 and a bottom roller 9, which is also part of foulard 1.In the exemplary embodiment, rollers 8, 9 are deflection-controlledrollers. Textile web 10 is guided from top to bottom, via a deflectionroller 6 arranged above bath surface 3 on the left side of trough 2 inFIG. 1, runs down into the dye bath, is deflected by 180° by deflectionroller 5, and leaves dye bath 4, going up, and then immediately passesthrough the pair of squeezing rollers 7. Rollers 8, 9 of the pair ofsqueezing rollers 7 exert a line force p per length unit of rollers 8,9, which is represented by arrows indicated with p. The effect ofpassing through the pair of squeezing rollers 7 is that the textile web10 has had the water removed from it, down to a certain moisturecontent, corresponding to a certain application of dye to textile web10, i.e. a certain amount of dye per surface unit of textile web 10.

The line force is understood to be the total force per cm of rollerlength exerted by rollers 8, 9 in the roll nip. The resulting linepressure in the roll nip depends on the width of the roll nip in thedirection of movement of the textile web. The line pressure is differentat every location of the roll nip, seen in the direction of movement ofthe textile web, and has an approximately parabola-shaped progression,with the maximum in the center.

The line force of pair of squeezing rollers 7 can be changed as textileweb 10 passes through, as indicated by the small crosswise arrows 12.Here, the change as a function of the textile web length is relevant.The line force profile in the direction of the textile web width is notof interest. It is selected in such a way that the moisture becomes asconstant as possible in the direction of the textile web width. Whenspeaking of “the” line force, this means an average value over the widthof the textile web. It is therefore supposed to be possible to adjustthis average value in variable manner over the length of textile web 10,in order to achieve uniform dye application to textile web 10 in thelengthwise direction.

At the beginning of a lot, there is a certain amount of dye bath 4 intrough 2. The concentration of treatment medium, i.e. of dye, in thisdye bath is determined continuously in some suitable manner, using ameasurement device 13, which is constantly connected with a regulationdevice 20, via a measurement line 14. This regulation device 20 controlsthe amount of the mean linear force of pair of squeezing rollers 7, as afunction of the signal of measurement device 13, as indicated by thedot-dash connecting line 15.

When a lot starts to pass through device 100 and the concentration ofthe dye in dye bath 4 changes, as determined by measurement device 13(e.g. optically), regulation and control device 20 sets a different lineforce of pair of squeezing rollers 7, according to a predeterminedalgorithm, i.e. a calculated algorithm or an algorithm experimentallydetermined in a test run, which establishes a relationship between aconcentration change that occurs at a certain concentration and the lineforce change which is necessary to maintain the amount of dye applied totextile web 10. If, for example, the concentration drops, the line forceis also lowered, so that more dye bath and therefore more dye remains ontextile web 10, once it has left pair of squeezing rollers 7. The goalis to keep the amount of dye applied to textile web 10 per surface unitof textile web 10 constant, in spite of concentration changes of dyebath 4 in trough 2.

FIG. 2 to 3 a show a process in which the adjustement of pair ofsqueezing rollers 7 is made dependent on the length of textile web thathas passed through. Device 200 of FIG. 2 agrees with device 100 of FIG.1 with regard to foulard 1, and therefore has the same reference numbersin this regard. According to FIG. 2, measurement device 13 is connectedwith a recording device 30, which detects the progression of theconcentration of dye bath 4 as a function of the length of textile webthat has passed through, via a line 14′, and records it on a data medium40, which can be removed from recording device 30 at an output device31, once the lot has passed through.

On a first segment of a textile web 10 of a certain material, with aspecific dye bath 4, a specific temperature and working speed, theconcentration progression over the length of the segment is measured,where the line force is kept constant in pair of squeezing rollers 7, asindicated by the absence of crosswise arrows 12 (see FIG. 1) in FIG. 2.

Then, a relationship according to FIG. 2a is obtained over length L ofthe textile web that has passed through. Here, the line force p, on theone hand, and the concentration c(L) in the trough (2), on the otherhand, are entered on the ordinate, while the length L of the textile webthat has passed through is entered on the abscissa. The line force p(L)is constant. However, the concentration of dye bath 4 in trough 2changes. In the exemplary embodiment shown with solid lines, it isassumed that textile web 10 extracts the dye more in the initial phase,so that the dye concentration drops over length L. The oppositeprogression is also possible, however, so that c′(L) increases, as shownin FIG. 2a with a broken line.

The concentration progression c(L) is converted, in recording device 30,using a predetermined algorithm, into a reference progression of theline force p(L), which is suitable for balancing out the difference inthe amount of dye applied to textile web 10 which can be expected due tothe concentration change, i.e. for assuring a uniform applied amount.

The reference progression p(L) of the line force is stored in memory inrecording device 30, on a data medium 40, which can be removed at 31after the lot has passed through, and duplicated if necessary. Thedrawing is to be understood as a schematic drawing. In practice,creation of data medium 40 can also be done in a different way.

The measurement using a test lot at constant line pressure as describedabove, and the determination of the reference progression, can becarried out in a laboratory or in a technical-scale facility, outside ofthe finishing company. The reference progression p(L) recorded on datamedium 40 holds true for all instances of a specific material of textileweb 10, a specific dye bath, and specific treatment parameters.

A finishing company has a device 300 according to FIG. 3, which agreeswith device 100 in terms of foulard 1, i.e. contains a pair of squeezingrollers 7 with an adjustable line force p. 200 and 300 can also be oneand the same device, if measuring of the test lot and production takeplace at the same location. The line force is then merely kept constantduring recording of the reference progression.

In the exemplary embodiment shown, measurement device 13 is not presentin device 300. Of course it can be present but simply not used.

Device 300 contains a regulation device 50 for regulating the line forceprogression over the textile web length in accordance with the referenceprogression determined according to FIG. 2 and stored on data medium 40.Regulation device 50 is connected with the two rollers 8, 9 of pair ofsqueezing rollers 7, via line 15, which can be used to pass signals tochange line force p to rollers 8, 9. Regulation device 50 has an inputdevice 51, into which data medium 40 can be inserted. On the basis ofthe data stored on data medium 40, the line force progression of pair ofsqueezing rollers 7 is regulated along the reference progression, insuch a way that the amount of treatment medium, i.e. dye applied totextile web 10 after it leaves pair of squeezing rollers 7 remainsconstant over the length of textile web 10.

These relationships are reproduced in the diagram of FIG. 3a.Concentration c(L) of treatment medium, i.e. dye on textile web 10 isconstant over length L of the textile web that has passed through.Reference progression p(L) of the line pressure drops in the assumedexemplary embodiment, in which concentration c(L) in trough 2 alsodrops. In the other case, that is if the concentration in the troughincreases, the broken-line progression p′(L) is maintained. This ishandled in such a way that the reference progression is determined oncefor every fabric and for a certain treatment of such fabric. Whenever anew lot of the same material is to be dyed under the same conditions,data medium 40 is brought out and used to regulate device 300. This canbe done at a different location than the location at which data medium40 was created, and, if data medium 40 has been duplicated, even atseveral locations at the same time.

Device 400 of FIG. 4a also corresponds, as far as the foulard isconcerned, to the one in FIG. 1, and has the same reference numberswhere this applies. Foulard 1 contains a pair of squeezing rollers 7, atwhich line force p can be adjusted in accordance with arrows 12.

There is no measurement device on trough 2. Instead, the progression ofline force p over length L of textile web 10 is controlled, instead,according to a predetermined length function. The control device isindicated with 60. Here, the progression of line force p over the lengthof the textile web is predetermined in some form, as reproduced by curve61 reproduced in the small dot-dash rectangle. In the exemplaryembodiment, the line force therefore increases in linear manner, andthen assumes a stationary value. This holds true for the case that theconcentration of dye bath 4 in trough 2 increases at first, as the lotpasses through, i.e. for the case that the fabric tends to absorb morewater, due to swelling or the like. In the opposite case, the line forcewould have to be lowered over the initial length of the lot.

The relationships are reproduced again in FIG. 4a, in the form of adiagram, which shows the progression of line force p, on the one hand,and concentration c of dye in the treatment liquid in trough 2, on theother hand, over length L of the textile web that has passed through.

The case where concentration c, shown with a broken line, in trough 2decreases over length L of the textile web that has passed through, isshown.

In order to balance this out exactly, i.e. to achieve a constant amountof dye applied per surface unit on textile web 10, in spite of this dropin trough 2, the line pressure would have to progress according to curvep_(th)(L), shown with a thin line.

This theoretical curve p_(th)(L) is not regulated, however, but ratherapproximated with a control mechanism.

Curve p₁(L) represents an approximation of the rising part of curvep_(th)(L) in three linear pieces p_(1′)(L), p_(1″)(L), and p_(1′″)(L).Subsequently, curves p_(th)(L) and p₁(L) make a transition into aconstant line force over length L.

Practice has shown, however, that in many cases an approximation of therising part of curve p_(th)(L) is possible with a single linear segment,which is reproduced by curve p₂(L).

Experience has shown that differences of five percent in the amount ofdye applied to the textile web can be detected using measurementtechnology, but are no longer perceived by the naked eye. As long ascurves p₁(L) and/or p₂(L) do not deviate from the ideal curve p_(th)(L)by more than five percent, this approximation is adequate in practice.

The selection of the incline and the location of the linearapproximation progressions are determined from empirical values.

What is claimed is:
 1. A process for treatment of a textile web with atreatment liquid containing a treatment medium, in which the textile webis continuously guided through a trough which contains the treatmentliquid, and subsequently passes through a pair of squeezing rollers,comprising the steps of: using a test textile web to measure theconcentration progression of the treatment liquid in the trough at aconstant line force of the pair of squeezing rollers, as a function ofthe length of textile web that has passed through; using thisinformation to determine a reference progression of the line force overthe length of textile web that has passed through, using a previouslydetermined relationship between a concentration change in the trough andthe line force change of the pair of squeezing rollers necessary tobalance it out, in such a way that the amount of applied treatmentmedium per surface unit of the textile web remains constant over thelength of the textile web; treating a length of production textile webthat is made of the same material, using the same treatment liquid andunder the same treatment parameters, wherein when the treatment liquidis applied to the length of textile web, the line force of the pair ofsqueezing rollers is regulated on the basis of the referenceprogression.
 2. The process according to claim 1, wherein the referenceprogression of the line force for a specific textile web and a specifictreatment liquid under specific treatment parameters is recorded on adata medium as the test textile web passes through, which is availableto regulate the line force progression of the pair of squeezing rollersin the treatment of production textile webs.
 3. A device for treatmentof a textile web with a treatment liquid, comprising: a trough forcontaining the treatment liquid, through which the textile web can bepassed continuously over its length; a pair of squeezing rollers locatedoutside of the area of the trough that contains the treatment liquid,the squeezing rollers having an adjustable line pressure through whichthe textile web can be passed after it leaves the treatment liquid inthe trough; a measurement device for measuring the concentration of thetreatment liquid in the trough; a recording device, connected with themeasurement device for recording a reference progression of the lineforce of the pair of squeezing rollers from the concentrationprogression in the trough as the textile web passes through at aconstant force of the pair of squeezing rollers, taking the relationshipinto account; a memory device for storing this relationship between aconcentration change in the trough and the line force change of the pairof squeezing roller required to balance it out; and a regulation devicethat is not connected to the measurement device, by which the line forceof the pair of squeezing rollers can be adjusted as a function of therelationship stored in the memory device; wherein the line force can beregulated over the length of the textile web, as a function of thereference progression stored in memory, using the regulation device. 4.The device according to claim 3, wherein the recording device stores themeasured concentration progression on a data medium, which can be outputby the recording device and input into the regulation device and read bythe latter.
 5. A process for treatment of a textile web with a treatmentliquid containing a treatment medium, comprising the steps of:continuously guiding the textile web through a trough which containstreatment liquid; subsequently passing the textile web through a pair ofsqueezing rollers that exert a line force on the textile web that iscontrolled as a function of the length of textile web that has passedthrough the rollers, so as to provide a uniform amount of treatmentmedium applied over the length of the textile web, per surface unit ofthe textile web; and wherein the theoretical line force progressions(p_(th)(L)) over the length of the textile web, which would have to bemaintained on the basis of the concentration progression in the troughcontaining the treatment liquid, with the goal of uniform application ofthe treatment medium per surface unit of the textile web, isapproximated by the control.
 6. The process according to claim 5,wherein the theoretical line force progression (p_(th)(L)) isapproximated in linear or piece-by-piece linear manner.
 7. A device fortreatment of a textile web with a treatment liquid, comprising: a troughfor containing treatment liquid, through which the textile web can bepassed continuously over its length; a pair of squeezing rollersarranged outside of the treatment liquid located in the trough, saidsqueezing rollers being arranged to exert an adjustable line pressurethrough which the textile web can be passed after it leaves thetreatment liquid in the trough; and a control device, by which the lineforce (p) of the pair of squeezing rollers can be controlled over thelength of the textile web (L), according to a predetermined progression;wherein the theoretical line force progression (p_(th)(L)) over thelength of the textile web (L), which would have to be maintained on thebasis of the concentration progression in the trough containing thetreatment liquid in order to provide a uniform application of thetreatment medium per surface unit of the textile web over the length ofthe textile web (L), is approximated by the control device.
 8. Thedevice according to claim 7, Wherein the theoretical line forceprogression (p_(th)(L)) is approximated in linear or piece-by-piecelinear manner.
 9. An apparatus for treatment of a textile web with atreatment liquid, comprising: a first treatment station, comprising: atrough for containing the treatment liquid, through which a test lengthof textile web can be passed continuously over its length; a pair ofsqueezing rollers located outside of the area of the trough thatcontains the treatment liquid, the squeezing rollers having anadjustable line pressure through which the test length of textile webcan be passed after it leaves the treatment liquid in the trough; ameasurement device for measuring the concentration of the treatmentliquid in the trough; means for using measurements provided by themeasurement device to determine a function which determines thatvariation in spacing between the squeezing rollers which provides auniform degree of application of treatment to a length of textile web;means for recording this function in a memory medium; a second treatmentstation, comprising: a trough for containing the treatment liquid,through which a length of production textile web can be passedcontinuously over its length; a pair of squeezing rollers locatedoutside of the area of the trough that contains the treatment liquid,the squeezing rollers having an adjustable line pressure through whichthe production textile web can be passed after it leaves the treatmentliquid in the trough; a memory reader for reading the function from thememory medium; and a regulation device that is controlled by thefunction so read so as to alter the spacing between the rollers, andthereby provide an even level of treatment across the length of theproduction textile web.
 10. The device as set forth in claim 9, whereinone treatment station can serve as the first treatment station at afirst time, and as the second treatment station at a different time. 11.The process as set forth in claim 1, wherein the treatment medium is adye bath.
 12. The device as set forth in claim 3, wherein the treatmentmedium is a dye bath.
 13. The process as set forth in claim 5, whereinthe treatment medium is a dye bath.
 14. The device as set forth in claim7, wherein the treatment medium is a dye bath.
 15. The apparatus as setforth in claim 9, wherein the treatment medium is a dye bath.